My friend's fish has fin rot, and it looks black all on the edges and affected area of the fins... I'd put him in a hospital tank with clean water and watch him closely. My friend says hers has the fin rot almost completely go away with clean water actually, and a bit of medication should help too. :)

My friend's fish has fin rot, and it looks black all on the edges and affected area of the fins... I'd put him in a hospital tank with clean water and watch him closely. My friend says hers has the fin rot almost completely go away with clean water actually, and a bit of medication should help too. :)

I've rescued a few bettas with fin rot.
It's another reason why I did a partial water change earlier than usual.

I went to my friends to check up on Cal. Well, his energy has improved BUT he has completely lost his dorsal fin :'( And the grey is half way up his body. It also looks like he is loosing the slime on his body. I'm not sure wither to be happy or sad. I felt more sad because he basically looks like he is decaying. He is a very light green-ish blue/his fins are starting to get white as well.
I think he maybe getting worse and his energy maybe just from the meds?